Active immunization against gonadotropin-releasing hormone affects thymic T cell production, migration, and colonization in male rat lymphoid tissue

Active immunization against gonadotropin-releasing hormone (GnRH) inhibits animal reproduction and has become a friendly alternative to surgical castration, which has been reported to affect the proportion of thymic T cell subpopulations. The effects of active immunization against GnRH on T cell migration from the thymus to the periphery and T cell distribution in lymphoid tissues remain unclear. Here, we showed that active immunization against GnRH increased thymic size and weight, enlarged the number of thymocytes, and enhanced CD4⁺ recent thymic emigrants (RTEs) and CD8⁺ RTEs migration to the blood and spleen. Active immunization against GnRH had no significant effect on naïve CD4⁺, naïve CD8⁺, CD4⁺ memory/activated, or CD8⁺ memory/activated T cells. In addition, active immunization against GnRH increased the proportion of CD3⁺ T cells in the spleen and lymph nodes. The percentages of CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells in the blood, spleen, and lymph nodes were not significantly affected by GnRH immunization. Overall, these results enhance our understanding of thymic T cell production, migration, and colonization in rat lymphoid tissues affected by GnRH immunization.